Population Density and Abundance of the Northernmost Population of Cordulegaster heros (Anisoptera: Cordulegastridae) in Europe (Czech Republic) with Notes on Its Biogeographical Range

Abstract

Cordulegaster heros is a Balkan species with a disjunctive area extending into Central Europe. The population in the Chřiby Mts. in the southeastern Czech Republic is the northernmost population, and this population was intensively studied from 2010 to 2021 to establish basic data on its abundance. In the territory, the geomorphological characteristics of streams, characteristics of sediment in streams, habitat, emergence time, and period of flight were recorded, and population viability was evaluated. Larvae were recorded in 10 small forest streams (altitude of 235–426 m a.s.l.), with an average minimum width of 51.9 cm, an average maximum width of 177.7 cm, an average minimum depth of 6.5 cm, an average maximum depth (in pools) of 21 cm, and an average stream gradient of 1.9 grades. The sediments in each stream exhibited a grain size distribution with an average fraction less than 0.05 mm represented by 6.3%, a fraction of 0.05–0.1 mm represented by 21.1%, a fraction of 0.1–2 mm represented by 52.1%, a fraction of 2–5 mm represented by 12.1%, a fraction of 5–20 mm represented by 8%, and a fraction of 20+ mm represented by 0.3%. The larval abundance was 0.1–6.7 larvae per 1 m2 of suitable sediment. The emergence period was recorded from 28 May to 1 July. The emergence site was categorized as larvae-dominated plant leave (57% of cases), plant stalks (21%), and tree trunks (17%). Exuviae occurred at an average of 154 cm at horizontal distance from the shore and an average vertical height of 77 cm above the ground. The average total distance of larval movement was 205 cm. The flight period in 2021 was recorded from 15 June to 11 August with peak flight activity noted in the third week of June. The northernmost population of C. heros was evaluated as viable and stable.

Occurrence and Population Density of the Endemic Species Cordulegaster buchholzi (Anisoptera: Cordulegastridae) on the Cyclades Islands in Greece

“…The findings at that time were surprisingly included in the occurrence data of Cordulegaster insignis [1,15,17,18]. The occurrence of the Cordulegaster helladica buchholzi subspecies is later mentioned in literary records [4,5,[7][8][9][10], in the work of Schneider et al [11] the subspecies was assigned species status.…”

“…Cordulegaster buchholzi is a European or Greek endemic species with very small area, which includes the Cyclades Islands-Andros, Tínos and Náxos [2,8,19]. If its area were limited to the Cyclades Islands, its area would be only 1000 km 2 .…”

“…buchholzi inhabits from geomorphological characteristics point of view quite a different type of habitat compared to other species. In contrast to the Central European species, this species inhabits watercourses in the Cyclades, which are formed by boulder to rocky riverbeds, often without undergrowth of vegetation [28,29]. The most similar are the habitats of the species Cordulegaster picta in northern Greece [Holuša unpubl.].…”

“…Parnassos after Attica, the island of Euboia and the Cyclades Islands [2,3]. The subspecies C. helladica buchholzi was reported only from the islands of Andros, Naxos and Tínos [2,[4][5][6][7][8][9][10]. Most recently, however, Schneider et al [11] revised the taxonomic position of this subspecies on the basis of genetic analysis, where they established Cordulegaster buchholzi (Figure 1) as a species and moved the limits of occurrence towards central Greece-the Euboia peninsula and the Attica region.…”

A Special Issue on the Diversity, Ecology and Evolution of Dragonflies and Damselflies (Insecta: Odonata)

“…The article "Population density and abundance of the northernmost population of Cordulegaster heros (Anisoptera: Cordulegastridae) in Europe (Czech Republic) with notes on its biogeographical range" [12], focuses on a long term study focused on characterizing habitat preferences and population trends of the species Cordulegaster heros, a Balkan endemic species. The authors found that current habitat conditions ensure the persistence of this species' populations in its northernmost distribution area, which are therefore evaluated as viable and stable.…”